Not everyone's body is the same at 32, 42, or 66. I agree if you can't handle a 50cc it's best to move on to something else. For myself some days I can swing a 395 around, sometimes a 50cc saw is too much, and my right shoulder is getting near replacement time, too much baseball as a kid guess.
You are so right on that!
Been fortunate to only have stuck hand in lawn mower at 14, broke hand, hit a semi head on in 1977 shattered my left femur, hung in traction for a month in McLaren, two surgeries later, quadriceps re-attachment, splenectomy, contracted Hep-C from blood transfusions, vein stripping, full knee replacement in 2005, dealt with stasis ulcers on and off for 12+ years, unna boots, hep-c treatment that failed (have to read fine print in drug ads, if virus free for 100 days, you are cured), fractured 9 ribs on right side of rib case T-boned a pipe railing at Bond Falls, dealt with pulmonary embolism and left leg blood clots, Trap-eze filter installed. I can go on with painful things, like threaded rods being removed while awake, or liver biopsies, healing after cancerous tumor removal. Yea, I am in great shape compared to my neighbor who had polio as a child and deals with a non-functioning left leg daily. It's all about one's perspective, I do not cut for a living or go at it 12+ hours a day, get to cut when I feel like it and stop whenever I want.